GaN MOSFETs have become popular in the last few years for Class D switching applications, and while NuPrime has experimented with these devices, it concluded that the familiar silicon MOSFETs allow better control of an amp’s sonic character. The longer the ON time, the closer the signal is pulled to the voltage rail of the amp. The width of the square wave determines the MOSFET’s ON time. The audio signal is embedded in a stream of square waves, whose width is proportional to the signal’s amplitude. In a Class D amplifier the power MOSFETs only have two states of operation, ON and OFF. Be sure to slide it fully upward, if like me, you’re in a 120V country. Note that the amp is shipped with the voltage selector switch set to 230V. Both RCA and XLR inputs are provided on the rear panel. The front panel is rather sparse looking with a small power LED and a power switch on the left that’s well camouflaged and hard to pick out. Heavy for a Class D amp at a net weight of 23 pounds and sporting a power rating of 230Wpc into 8 ohms, it was ready to rock. Right out of the box it was clear that this $4995 stereo amplifier meant business. The Evolution STA amplifier is a prime example, nudging forward the state of the art in Class D amplification.

I n case you’re wondering, NuPrime Audio was founded in 2014 by Jason Lim, who previously co-founded NuForce Audio, with the express goal of continuing NuForce’s high-end product line.

Amp research power step